For some years, motors having rotors fitted with permanent magnets have been used for elevator drives. The rotors may be constructed as internal rotors with permanent magnets mounted on their outside, or as external rotors with permanent magnets mounted on their inside. The task of properly fitting the rotors with permanent magnets is a comparatively onerous one.
In a known method, plastic films or aluminum strips, for example, which have recesses having a shape of magnets are adhesively bonded to the rotor surface. An adhesive is then applied to the reverse of the magnets, and the magnets are placed individually in the recesses. Care has to be taken to ensure that the magnets have been inserted correctly and cleanly in their recesses in spite of their magnetic force, as they are strongly attracted to the rotor surface and are influenced by magnets that have already been positioned. As the magnets always have to be attached with a small gap from one magnet to the next, there is the danger of slippage, and the operator has to wait for the adhesive to cure on each magnet before the next magnet can be attached. Thus, this method of rotor manufacture is very time-consuming.
EP 1 255 343 A2 discloses a method in which magnets are arranged in a row on a ring. As many rings as are needed are for the motor are attached side by side on a basic ring body. This ensures that the rings comprising the magnets can be rotated through a small angle relative to one another, so as to reduce or completely eliminate surges in the true running of the motor at the beginning and end of the magnets. However, the fact that the magnets have to be individually fastened to the rings and that the rings have to be fixed to the base member with no imbalances continues to be a problem.
EP 1 605 574 A1 discloses prefabricating the pole surfaces by segmenting the rotor surface into pole surfaces to reduce manufacturing costs. However, a guided arm or servo positioner is needed for each pole around the rotor when assembling the finished rotor for each pole, which leads to a major expense if there are a number of poles. Additionally, the magnets still have to be applied to the pole surfaces and attached thereto.
There is a need to simplify and speed up the production of a rotor with permanent magnets, thereby significantly reducing the rotor's cost, particularly in elevator drive applications.